RT Journal Article SR Electronic T1 Covid-19 variants of concern and pregnancy JF BMJ Medicine JO bmjmed FD BMJ Publishing Group Ltd SP e000151 DO 10.1136/bmjmed-2022-000151 VO 1 IS 1 A1 Sarah J Stock A1 Clea Harmer A1 Clara Calvert YR 2022 UL http://bmjmedicine.bmj.com/content/1/1/e000151.abstract AB